The present disclosure relates generally to image producing machines, and more particularly to a solid phase change ink melter assembly and an image producing machine or printer including such an assembly.
In general, phase change ink image producing machines or printers employ phase change inks that are in a solid phase at ambient temperature, but exist in the molten or melted liquid phase (and can be ejected as drops or jets) at an elevated operating temperature of the machine or printer. At such an elevated operating temperature, droplets or jets of the molten or liquid phase change ink are ejected from a printhead device of the printer onto a printing media. Such ejection can be directly onto a final image receiving substrate, or indirectly onto an imaging member before transfer from it to the final image receiving media. In any case, when the ink droplets contact the surface of the printing media, they quickly solidify to create an image in the form of a predetermined pattern of solidified ink drops.
An example of such a phase change ink image producing machine or printer, and the process for producing images therewith onto image receiving sheets is disclosed in U.S. Pat. No. 6,905,201, issued on Jun. 14, 2005. The '201 patent discloses an image producing machine, such as the high-speed phase change ink image producing machine or printer 10 shown in FIG. 1 herewith. As illustrated, the machine 10 includes an imaging member 12, shown in the form of a drum, having an imaging surface 14 that is movable in the direction 16, and on which phase change ink images are formed.
The image producing machine 10 also includes a phase change ink delivery subsystem 20 that has at least one source 22 of one-color phase change ink in solid form. For a multicolor image producing machine, the ink delivery system 20 may include several sources, such as four sources 22, 24, 26, 28, representing four different colors CYMK (cyan, yellow, magenta, black) of phase change inks. The ink delivery system also includes a melting and control apparatus 300 (FIG. 2) for melting or phase changing the solid form of the phase ink into a liquid form, and then supplying the liquid form to a printhead system 30 including at least one printhead assembly 32. Since the phase change ink image producing machine 10 is a high-speed, or high throughput, multicolor image producing machine, the printhead system includes four separate printhead assemblies 32, 34, 36 and 38 receiving molten ink from a corresponding source 22, 24, 26 and 28.
As further shown, the machine 10 includes a substrate supply and handling system 40. Operation and control of the various subsystems, components and functions of the machine or printer 10 are performed with the aid of a controller or electronic control subsystem (ESS) 80. Details of these systems and subsystems can be obtained from the '201 patent. In operation, image data for an image to be produced is sent to the controller 80, such as from a scanning system 70, for processing and output to the printhead assemblies 32, 34, 36, 38. Appropriate color solid forms of phase change ink are melted and delivered to the printhead assemblies to form the image on the surface 14.
The '201 patent discloses a number of melter assemblies 300, as shown in FIG. 2 that includes a housing 302 with walls 304 defining a melting chamber 306. Each melter assembly 300 also includes a positive temperature coefficient (PTC) heating device 310 that is mounted within the melting chamber 306 for heating and melting solid pieces of phase change solid ink. Each housing 302 may include a screen device 314 that is mounted below the PTC heating device 310 for removing unwanted particles from the melted molten liquid ink coming from the heating device 310.
The PTC heating device 310 disclosed in the '201 patent includes a frame made of a conductive material such as aluminum, and a pair of folded fins 326, 328 that are also made of a conductive material such as aluminum. The folded fins 326, 328 act as a heating element for providing the heat and melting surface area that contact and melt the solid pieces phase change ink. A pair of electrodes connected the folded fins 322, 324 to an electrical supply. The folded fins define a series of channels between fin folds 332 that increase the heated surface area and therefore maximize the efficiency of the PTC heating device 310. The molten liquid ink drops gravitationally from the folded fins and through the channels to the molten liquid ink storage and control assembly 400 located below the melter assembly 300, as shown in FIG. 2.
As disclosed herein, the phase change ink printing process includes raising the temperature of a solid form of the phase change ink to melt the ink and form a molten liquid phase change ink. Conventionally, the solid form of the phase change is a “stick”, “block”, “bar” or “pellet” that is fed into a heated melting device, such as the device disclosed in the '201 patent. Due to the requirement for the phase change of the ink, image producing machines or printers of this type are considered to be low throughput, typically producing at a rate of less than 30 prints per minute (PPM). The throughput rate (PPM) of a phase change ink image producing machine is directly dependent on how quickly the “stick”, “block”, “bar” or “pellet” form can be melted down into a liquid.
There a prevailing need for higher throughput for phase change ink image producing machines or printers particularly color images on plain paper substrates.